As the progress of science and technology, glass covers are increasingly used in normal display screens of electronic products, for example cell phones, etc. A glass cover is typically an optical glass, and has the functions of protecting display modules, carrying touch control sensor layers or decorative layers, mechanism assembly carriers, etc.
The types of glass covers may be generally divided into types according to functions thereof: the conventional glass covers purely used for protecting display modules and the sensor glass covers as the carriers of touch control elements. In comparison, the function of a conventional glass cover is to protect a display module from being damaged by an external force, water vapor, particles, etc., such as a non-touch module glass cover, an in-cell glass cover, an on-cell glass cover; while a sensor glass cover is required to carry a sensor structure, for example an OGS glass, a GF glass, in addition to the protection of a display module from being damaged by an external force, water vapor, particles, etc. However, with respect to any glass cover, the initial protective function of a glass cover is an extremely important function.
As the development of the function of human-computer interaction, there is a trend of increasing demand for creating holes (these holes are, for example, microphone holes, HOME button holes, etc., and the shape of the holes may be a annular shape, an elongated shape, and the like) on a glass cover. Creating a hole on the glass cover will certainly damage the structure of the glass surrounding the through hole and brings about defects such as collapses, cracks, etc. Therefore, after a hole is created on the glass cover, the glass structure surrounding the through hole is required to be strengthened. With respect to a glass cover, the change in the structure at the edge will be caused in the process of cutting the glass cover, and therefore the edge of the glass cover is further required to be strengthened at the same time.
By classification according to the principles strengthening, the methods for strengthening glass covers are divided into two types, physical strengthening and chemical strengthening, and these two types of strengthening methods have the characteristics as follows.
Physical strengthening: the edge of the glass cover is polished by using a brush with a certain rigidity to reduce or eliminate defects such as collapses, cracks, etc., caused by cutting or edge grinding. This strengthening method has the disadvantage that since the size of the through hole is relatively small (taking a annular microphone as an example, the diameter of the through hole is typically 0.8 mm-1.2 mm), this method cannot strengthen the position of the through hole and is prone to cause the glass cover to begin to break down with the through hole desired to be strengthened as the center.
Chemical strengthening: a glass cover is soaked in a strong acid solution and the glass is etched with the strong acid solution so as to achieve the object of reducing or eliminating defects such as collapses, crack, etc. An OGS structure allows a touch control element to be produced on a glass surface. When chemical strengthening is performed, in order to prevent the touch control element from being damaged in the process of etching, an acid-resistant film, which is acid resistant, is required to be attached on the surface of the glass before chemical strengthening is performed to expose the position such as the edge, the through hole, etc., which is required to be strengthened. Theoretically, the method of chemical strengthening may strengthen the position of the through hole. However, due to the presence of the liquid surface tension between the glass and the strong acid at the through hole, the flowability of the acid liquid at the through hole is very poor and the etching speed of the strengthening of the through hole is obviously slower than the etching speed at the position of the edge, resulting in insufficient strengthening of the through hole. If the etching time is simply elongated, it will result in excessive strengthening of the edge.